1. Field of the Invention
The present invention relates to a power monitoring system for managing supply and reception of power between an electric vehicle such as an electric car and an out-of-vehicle apparatus.
2. Description of the Background Art
Electric vehicles (EV) include, for example, an electric car that obtains motive power by driving a motor using power charged in a secondary battery (hereinafter referred to as “battery”) as a drive source thereof, and a plug-in hybrid electric vehicle (PHEV) that adopts an engine and a motor in combination. As a method for charging power to the battery of the EV, for example, there may be mentioned a method in which AC system power is supplied from a household socket or the like and the AC is converted into DC by an in-vehicle charger and then supplied to the battery, or a method in which DC power is directly supplied to the battery from an out-of-vehicle apparatus, such as a charging station, provided outside the vehicle EV.
Moreover, in recent years, a method has been considered in which, for an efficient utilization of renewable energy obtained by solar power generation, wind power generation, or the like, the renewable energy is utilized through a next-generation power network called a smart grid, and an EV is incorporated therein.
For example, it has been considered that excess power resulting from power generation of the renewable energy mentioned above is stored in the battery of the EV so that the stored power is utilized in a household or in a factory as necessary or is sold to a power company.
In a case of charging the EV or supplying power from the EV to the smart grid, the amount of power measured by the out-of-vehicle apparatus such as the charging station and the amount of power measured by the EV may be different from each other due to, for example, an abnormal condition such as power exploitation made by a malicious user or short-circuit of a cable. In such a case, there is a possibility that a trouble about a bill payment occurs.
In a method for measuring the amount of power in each of the out-of-vehicle apparatus and the EV, in general, the out-of-vehicle apparatus uses a power meter provided within the apparatus while the EV uses power information obtained from a battery management unit that is provided near the battery and constantly monitors a state of the battery.
In this method, however, the EV measures the power at a battery terminal. Therefore, no consideration is given to power consumption in the EV itself caused by, for example, operating equipments, such as an air conditioner and accessories, arranged between a power feed port of the EV and the battery terminal. Thus, a problem arises that a difference occurs between the amount of power measured in the out-of-vehicle apparatus and the amount of power measured in the EV.
A technique for solving such a problem is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-234882. In the technique disclosed in Japanese Patent Application Laid-Open No. 2008-234882, power meters are provided in both a power feed apparatus (out-of-vehicle apparatus) and an electric vehicle so that power measurement information of both of them are compared with each other.